omap: rx51: Don't power up speaker amplifier at bootup

Speaker amplifier is accidentally powered up in early TWL gpio setup. This
causes a few mA of needless battery current consumption. Without this patch
the amplifier can be shutdown only by having one active audio playback and
shutdown cycle to speaker output.

Thanks to Kalle Jokiniemi <kalle.jokiniemi@nokia.com> for noticing the issue.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Cc: Kalle Jokiniemi <kalle.jokiniemi@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>